Took ages, unfortunately, to stifle very loud howlers (6)
I believe the answer is:
gaffes
'howlers' is the definition.
Although both the answer and definition are plural nouns, I cannot see how one could define the other.
'took ages unfortunately to stifle very loud' is the wordplay.
I cannot quite see how this works, but
'loud' could be 'ff' (short for fortissimo - 'very loud' in music) and 'ff' is found in the answer.
an anagram of 'ages' is 'gaes' which is within the remaining letters.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for gaffes that I've seen before include "Social blunders, often of speech" , "Socially embarrassing actions or remarks" , "bloomers" , "Faux pas" , "Embarrassing blunders" .)